A triangular cantilever plate is subjected to its own weight. Compute the lowest three natural frequencies of the plate.

The plate is 6.0 inches by 6.0 inches and the thickness is 0.034 inches. The weight density is 0.06414 lb/in3. The elastic modulus of the material is 6,500,000 lb/in2 and Poisson's ratio is 0.3541.

The model used has 66 joints and 55 plate elements. The joints 1 to 11 are fixed in all six (6) degrees of freedom. Since the plate elements do not have any stiffness about the axis perpendicular to the plane of the plate, the rotation about the global Z-axis for joints 12 to 66 are eliminated.

The joint masses are automatically computed by LARSA. The material and sectional property data of the plate structure are given as:

Modulus of Elasticity = 6,500,000 lb/in2

Poisson Ratio = 0.3541

Shear Modulus = 2,400,118 lb/in2

Height of Triangle = 6.0 inch

Plate Thickness = 0.034 inch

Weight Density = 0.06414 lb/in3 g = 386 in/sec3

Tested Features

Reference

"ASME Pressure Vessel and Piping 1972 Computer Programs Verification.", I.S. Tuba and W.B. Wright, ASME publication, I-24, Problem 2.

Sources

LARSA 4D
COSMOS7
NASTRAN

Results Comparison

App Link:

https://openbrim.org/objid0dg65daa4qyy465ktloyln.project

Library Link:

https://openbrim.org/objidy1fhvnvaw1fsxjyp3ivxt.libobj

Model	Output Parameter	OpenBrIM	LARSA	COSMOS7	NASTRAN	OpenBrIM vs LARSA
Triangular cantilever plate	f1(hz)	55.42	55.5	55.6	55.6	0.81%
	f2(hz)	203.98	204.23	206.5	206.5	0.17%
	f3(hz)	279.08	281.33	283.1	283.2	0.13%

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